<html>
<meta http-equiv='Content-Type' content='text/html;charset=UTF-8'/>
<style>
.halfStyle {
    position:relative;
    display:inline-block;
    font-size:20px; /* or any font size will work */
    color: transparent; /* hide the base character */
    overflow:hidden;
    white-space: pre; /* to preserve the spaces from collapsing */
}
.halfStyle:before { /* creates the left part */
    display:block;
    z-index:1;
    position:absolute;
    top:0;
    width: 30%;
    content: attr(data-content); /* dynamic content for the pseudo element */
    overflow:hidden;
    pointer-events: none; /* so the base char is selectable by mouse */
    color: #f00; /* for demo purposes */
    text-shadow: 2px -2px 0px #af0; /* for demo purposes */
}
.halfStyle:after { /* creates the right part */
    display:block;
    direction: rtl; /* very important, will make the width to start from right */
    position:absolute;
    z-index:2;
    top:0;
    left:20%;
    width: 30%;
    content: attr(data-content); /* dynamic content for the pseudo element */
    overflow:hidden;
    pointer-events: none; /* so the base char is selectable by mouse */
    color: #000; /* for demo purposes */
    text-shadow: 2px 2px 0px #0af; /* for demo purposes */
}
</style>
<body>
	<button class="halfStyle" data-content="Hello" witdh = "200px">Hello</button>
</body>
</html>